Systems and methods for analyte sensing in physiological gas samples

ABSTRACT

Embodiments herein relate to systems and devices for measuring analyte presence on graphene varactors, which can be used for analyte sensing in physiological gas samples. In an embodiment, a system for measuring analyte presence on a graphene varactor is included having a capacitance to digital converter (CDC) and a graphene varactor. The CDC can be in electrical communication with the graphene varactor and can be configured to measure the capacitance of the graphene varactor in response to an excitation signal over a plurality of DC bias voltages. Other embodiments are also included herein.

This application is a continuation of U.S. application Ser. No. 16/037,218, filed Jul. 17, 2018, which claims the benefit of U.S. Provisional Application No. 62/533,916, filed Jul. 18, 2017, the contents of which are herein incorporated by reference in their entirety.

FIELD

Embodiments herein relate to systems and devices for analyte sensing in physiological gas samples. More specifically, embodiments herein relate to systems and devices for measuring analyte presence on graphene varactors.

BACKGROUND

In the process of providing health care, clinicians often make physical observations and run tests to gather data about a patient. After collecting data and analyzing other aspects, such as a given patient's health history, the clinician often forms a diagnosis and then selects a therapy to treat the diagnosed condition.

Knowledge of the presence and/or concentrations of various chemical analytes, such as volatile organic compounds, can be extremely useful in forming a diagnosis. However, measuring such chemical analytes in a clinically practical manner remains technically challenging.

SUMMARY

Embodiments herein relate to systems and devices for analyte sensing in physiological gas samples.

In a first aspect, a system for measuring analyte presence on a graphene varactor is included. The system can include a capacitance to digital converter (CDC) and a graphene varactor. The CDC can be in electrical communication with the graphene varactor and can be configured to measure the capacitance of the graphene varactor in response to an excitation signal over a plurality of DC bias voltages.

In a second aspect, in addition to or in place of other aspects herein, the system can further include a multiplexor configured to selectively provide electrical communication between the CDC and a plurality of graphene varactors.

In a third aspect, in addition to or in place of other aspects herein, an excitation signal can be applied to a selected graphene varactor through the multiplexor.

In a fourth aspect, in addition to or in place of other aspects herein, the excitation signal can include an alternating voltage component.

In a fifth aspect, in addition to or in place of other aspects herein, the amplitude of the excitation signal is fixed by the CDC.

In a sixth aspect, in addition to or in place of other aspects herein, a controller circuit can be included and can be configured to receive an electrical signal reflecting the capacitance of the graphene varactor.

In a seventh aspect, in addition to or in place of other aspects herein, the controller circuit can include a microcontroller.

In an eighth aspect, in addition to or in place of other aspects herein, the system further includes an electronic component in electrical communication with the controller circuit and the CDC, the electronic component selected from the group consisting of an I2C or an SPI.

In a ninth aspect, in addition to or in place of other aspects herein, the graphene varactor can include a functionalized graphene varactor.

In a tenth aspect, in addition to or in place of other aspects herein, the controller circuit is configured to calculate at least one parameter for the graphene varactor selected from the group consisting of maximum slope of capacitance to voltage; change in maximum slope of capacitance to voltage over a baseline value; minimum slope of capacitance to voltage; change in minimum slope of capacitance to voltage over a baseline value; minimum capacitance; change in minimum capacitance over a baseline value; voltage at minimum capacitance; change in voltage at minimum capacitance; maximum capacitance; change in maximum capacitance; ratio of maximum capacitance to minimum capacitance; response time constant; and ratios of any of the foregoing between the graphene varactor and a second graphene varactor.

In an eleventh aspect, in addition to or in place of other aspects herein, the graphene varactor(s) are grounded.

In a twelfth aspect, in addition to or in place of other aspects herein, the graphene varactor(s) are in electrical communication with an independent excitation output of the CDC.

In a thirteenth aspect, in addition to or in place of other aspects herein, the system can further include one or more programmable digital to analog converters (DACs) in series with the plurality of graphene sensors.

In a fourteenth aspect, in addition to or in place of other aspects herein, the system can further include a switch, the CDC in electrical communication with the switch and controlling the switch to selectively provide communication with output voltages of two programmable digital to analog converters (DACs), the programmed voltage difference between the DACs determining the excitation amplitude, and the difference between the programmed average voltage of the DACs and the bias at the CDC input determining the DC bias.

In a fifteenth aspect, a method for measuring analyte presence on a graphene varactor is included. The method can include measuring a capacitance of the graphene varactor over a range of DC bias voltages; comparing the measured capacitance at one or more DC bias voltages to one or more corresponding baseline capacitance values; and determining the presence or absence of an analyte based on the comparison.

In a sixteenth aspect, in addition to or in place of other aspects herein, the method can further include determining one or more aspects selected from the group consisting of maximum slope of capacitance to voltage; change in maximum slope of capacitance to voltage over a baseline value; minimum slope of capacitance to voltage; change in minimum slope of capacitance to voltage over a baseline value; minimum capacitance; change in minimum capacitance over a baseline value; voltage at minimum capacitance; change in voltage at minimum capacitance; maximum capacitance; change in maximum capacitance; ratio of maximum capacitance to minimum capacitance; response time constant; and ratios of any of the foregoing between two different graphene sensors.

In a seventeenth aspect, in addition to or in place of other aspects herein, the method can further include forming a capacitance to voltage curve from the measured capacitance of the graphene varactor over the range of DC bias voltages.

In an eighteenth aspect, in addition to or in place of other aspects herein, the method can further include comparing the formed capacitance to voltage curve with a baseline capacitance to voltage curve.

In a nineteenth aspect, in addition to or in place of other aspects herein, the method can further include distinguishing between different analytes binding to the graphene varactor.

In a twentieth aspect, in addition to or in place of other aspects herein, the range of DC bias voltages is from −3 V to 3 V.

This summary is an overview of some of the teachings of the present application and is not intended to be an exclusive or exhaustive treatment of the present subject matter. Further details are found in the detailed description and appended claims. Other aspects will be apparent to persons skilled in the art upon reading and understanding the following detailed description and viewing the drawings that form a part thereof, each of which is not to be taken in a limiting sense. The scope herein is defined by the appended claims and their legal equivalents.

BRIEF DESCRIPTION OF THE FIGURES

Aspects may be more completely understood in connection with the following drawings, in which:

FIG. 1 is a schematic view of various components of a system in accordance with various embodiments herein.

FIG. 2 is a schematic exploded view of a graphene varactor in accordance with various embodiments herein.

FIG. 3 is a schematic cross-sectional view of a graphene varactor in accordance with various embodiments herein.

FIG. 4 is a schematic cross-sectional view of elements of a gas sensing device consistent with the technology disclosed herein.

FIG. 5 is a schematic diagram of circuitry to measure the capacitance of a plurality of graphene sensors in accordance with various embodiments herein.

FIG. 6 is a schematic diagram of circuitry to measure the capacitance of a plurality of graphene sensors in accordance with various other embodiments herein.

FIG. 7 is a schematic diagram of circuitry to measure the capacitance of a plurality of graphene sensors in accordance with various other embodiments herein.

FIG. 8 is a graph showing capacitance versus DC bias voltage for a graphene varactor in accordance with various embodiments herein.

FIG. 9 is a graph showing capacitance versus DC bias voltage for a graphene varactor in accordance with various embodiments herein.

FIG. 10 is a graph showing capacitance versus DC bias voltage for a functionalized graphene varactor in response to acetone binding in accordance with various embodiments herein.

FIG. 11 is a graph showing capacitance versus DC bias voltage for a functionalized graphene varactor in response to octane binding in accordance with various embodiments herein.

FIG. 12 is a graph showing capacitance versus DC bias voltage for a functionalized graphene varactor in response to octanol binding in accordance with various embodiments herein.

While embodiments are susceptible to various modifications and alternative forms, specifics thereof have been shown by way of example and drawings, and will be described in detail. It should be understood, however, that the scope herein is not limited to the particular embodiments described. On the contrary, the intention is to cover modifications, equivalents, and alternatives falling within the spirit and scope herein.

DETAILED DESCRIPTION

Volatile organic compounds, as sensed in breath samples or other gas samples, can provide valuable information about the health status of a patient. In particular, patterns of volatile organic compounds (including the presence, absence, and/or concentration of a plurality of different volatile organic compounds) in a breath or gas sample of a patient can be associated with various disease states and/or particular health statuses. The disease states can include, but are not limited to, lung cancer, colon cancer, pulmonary disease (e.g. asthma, COPD), cardiovascular disease (e.g. heart failure), infectious diseases, digestive and inflammatory diseases (e.g. inflammatory bowel diseases such as Crohn's, colitis, or the like) or diabetes.

Graphene varactors are one type of device that can be used to measure volatile organic compounds. Various properties of graphene varactors, such as capacitance, can change in response to the presence of volatile organic compounds thereon. However, measurement of properties of the graphene varactors, such as capacitance, remains technically challenging.

However, embodiments herein can be used to rapidly and accurately measure the capacitance of a plurality of graphene varactors.

Referring now to FIG. 1 , a schematic view is shown of possible components of a system 100 in accordance with various embodiments herein. The system 100 can include a breath sensing device 160 for sensing gaseous analytes (or volatile organic compounds) in accordance with various embodiments herein. In this embodiment, the system is in a hand-held format. It will be appreciated, however, that many other formats for the system are contemplated herein.

The breath sensing device 160 can include a housing 178. The breath sensing device 160 can include a mouthpiece 162 into which a subject to be evaluated can blow a breath sample. The breath sensing device 160 can also include a display screen 174 and a user input device 176, such as a keyboard. The breath sensing device 160 can also include a gas outflow port 172. Aspects of breath sensing systems and devices are described in U.S. Publ. Appl. No. 2016/0109440, the content of which is herein incorporated by reference. While FIG. 1 shows a breath sensing device, it will be appreciated that other types of gas sampling systems can also be used herein. For example, gas sampling devices for use with catheters and endoscopy systems can also be used. An exemplary gas sampling device in the context of a catheter or endoscopy device is described in U.S. Appl. No. 62/350,345, the content of which is herein incorporated by reference.

In some embodiments, the system 100 can include a local computing device 182 that can include a microprocessor, input and output circuits, input devices, a visual display, a user interface, and the like. In some embodiments, the breath sensing device 160 can communicate with the local computing device 182 in order to exchange data between the breath sensing device 160 and the local computing device 182. The local computing device 182 can be configured to perform various processing steps with the data received from the breath sensing device 160, including, but not limited to, calculating various parameters described herein. However, it should be appreciated that in some embodiments the features associated with the local computing device 182 can be integrated into the breath sensing device 160. In some embodiments, the local computing device 182 can be a laptop computer, a desktop computer, a server (real or virtual), a purpose dedicated computer device, or a portable computing device (including, but not limited to, a mobile phone, tablet, wearable device, etc.).

The local computing device 182 and/or the breath sensing device 160 can communicate with computing devices in remote locations through a data network 184, such as the Internet or another network for the exchange of data as packets, frames, or otherwise.

In some embodiments, the system 100 can also include a computing device such as a server 186 (real or virtual). In some embodiments, the server 186 can be located remotely from the breath sensing device 160. The server 186 can be in data communication with a database 188.

The database 188 can be used to store various patient information, such as that described herein. In some embodiments, the database can specifically include an electronic medical database containing data regarding the health status of a patient, patterns of data associated with various conditions (such as that generated from machine learning analysis of large sets of patient data), demographic data and the like.

Graphene varactors can be prepared in various ways and with various geometries. Referring now to FIG. 2 , an exploded view of a graphene varactor 200 is shown. The graphene varactor 200 can include an insulator layer 202, a gate electrode 204, a dielectric layer 206, a graphene layer 208, and a contact electrode 210.

FIG. 3 shows a cross-sectional view of the graphene varactor 200. As is shown, the gate electrode 204 can be recessed into the insulator layer 202. The gate electrode 204 can be formed by etching a depression into the insulator layer 202 and then depositing an electrically conductive material in the depression to form the gate electrode 204. The insulator layer 202 can include various materials. In some embodiments the insulator layer 202 can be silicon dioxide formed on a silicon substrate (wafer). The dielectric layer 206 can be formed on a surface of the insulator layer 202 and the gate electrode 204. In some examples, the dielectric layer 206 can be formed of a material, such as, silicon dioxide, aluminum oxide, hafnium dioxide, zirconium dioxide, hafnium silicate or zirconium silicate. The graphene layer 208 can be disposed on the dielectric layer 206. In some aspects, the graphene layer 208 can be a graphene monolayer. A contact electrode 210 can also be disposed on the surface (or a portion thereof) of the graphene layer 208. Aspects of exemplary graphene varactors can be found in U.S. Publ. App. No. 2014/0145735, the content of which is herein incorporated by reference. Further aspects of gas and/or breath sampling systems are described in U.S. Publ. Appl. No. 2016/0109440, the content of which is herein incorporated by reference.

In various embodiments, the graphene layer can be functionalized to make the graphene sensor specific for a particular analyte or class of analytes. As analytes bind to the graphene layer, the capacitance of the sensor changes. Further, as shown below with regard to FIGS. 8-9 , the capacitance changes differently based on the voltage of the excitation current.

Systems herein can also include a breath and/or gas sensing device or system. In particular, systems herein can gather data on the presence, absence, and/or amount of various gaseous analytes including, but not limited to, volatile organic compounds. FIG. 4 is a schematic cross-sectional view of an example system 400 consistent with the technology disclosed herein. It will be appreciated that this schematic view has been simplified for ease of illustration and that embodiments of systems and devices herein can include various features not shown in FIG. 4 . In addition, some embodiments of systems and devices herein may lack various features shown in FIG. 4 . The system 400 is generally configured for collecting a gas sample and communicating data associated with the gas sample. The system 400 has a gas sampling device 410 and a docking station 430.

The gas sampling device 410 can be configured to collect a gas sample and facilitate testing of the gas sample to generate data. In some embodiments, the gas sampling device 410 can be configured as a handheld device. In such cases, the gas sampling device can be configured to be held in the hand of a care provider, a patient, or both, during certain steps of its use, while also being configured to be held or otherwise positioned in association with the docking station 430 during certain steps of its use.

In some embodiments, the gas sampling device 410 is configured to receive a gas sample, such as exhaled breath, from a patient and direct the gas sample to a testing location. The gas sampling device 410 generally has a housing 420 defining an airflow aperture 422, a gas testing chamber 426, a sensor receptacle 428, an airflow pathway 424, and a docking structure 421.

When receiving a gas sample, the gas (such as breath from a patient), can pass into the gas sampling device 410 through the airflow aperture 422, through the airflow pathway 424, into the gas testing chamber 426 and into contact with one or more measurement zones 442 of a disposable sensor test strip 440, and then out the end of the gas testing chamber 426 through the sensor receptacle 428, or through a separate exhaust port (not shown in this view). While this view depicts contact in some areas between the sensor receptacle 428 and the disposable sensor test strip 440, it will be appreciated that there can be segments or areas where the sensor receptacle 428 and the disposable sensor test strip 440 do not contact or do not create sealing contact, thus allowing for a path for the gas to flow out through the sensor receptacle 428.

While FIG. 4 shows the airflow pathway 424 to be approximately the same size as the interior space of the housing 420, it will be appreciated that this is simply for ease of illustration and that the size of the airflow pathway 424 can be, in many cases, much smaller than the entire interior size of the housing 420, allowing for room for other components within the interior of the housing 420, such as other components described herein including, but not limited to, sensors, a power source, processing devices, communication hardware, conditioning elements, and the like.

The housing 420 can be constructed of a variety of materials and combinations of materials. The housing 420 can be a single cohesive structure or can be constructed of multiple components that are coupled to form the housing 420. As an illustrative example, a portion of the housing 420 that defines the airflow pathway 424 can be coupled to the portion of the housing 420 that defines the airflow aperture 422. The portion of the housing 420 that defines the airflow pathway 424 can include a conduit or tube with various different cross-sectional sizes and shapes. The conduit or tube can be formed from various materials including, but not limited to, polymers, metals, ceramics, glass, composites or the like. In some embodiments, surfaces lining the airflow pathway 424 can be coated with materials to provide various desirable functional properties.

The airflow aperture 422 is generally configured to provide an input for the gas sample at the housing 420. In some embodiments the airflow aperture 422 is configured to be in fluid communication with a patient's mouth, although in some other embodiments a protective liner can be used to provide a barrier between the patient's mouth and the housing, which will be described in more detail, below.

The airflow pathway 424 generally is configured to direct the gas input at the airflow aperture 422 to the gas testing chamber 426. As such, the airflow pathway 424 generally extends from the airflow aperture 422 to the gas testing chamber 426. The airflow pathway 424 can have a cross-sectional area that is substantially the same along the length of the airflow pathway or it can vary. In some embodiments, the gas testing chamber 426 can have different interior dimensions (e.g., height, width, etc.) than the airflow pathway leading to it.

The gas testing chamber 426 defines a testing location for the gas sample. In various embodiments, the gas testing chamber 426 is configured to receive a measurement zone 442 of a disposable sensor test strip 440. Accordingly, the sensor receptacle 428 defined by the housing 420 is generally configured to removably retain the disposable sensor test strip 440 within the gas testing chamber 426. In various embodiments the sensor receptacle 428 is configured to slidably receive the disposable sensor test strip 440 that is manually inserted by a user. In some embodiments, the disposable sensor test strip 440 can be inserted with its long (or major) axis parallel to the long (or major) axis of the housing 420. However, in other embodiments, the disposable sensor test strip 440 can be inserted with its long (or major) axis positioned differently with respect to the long (or major) axis of the housing 420, such as perpendicular. Example sensor test strips will be described in more detail, below.

While FIG. 4 depicts the test strip located approximately in the middle of the gas sampling device 410 (top to bottom with regard to the perspective of the figure), it will be appreciated that the test strip can be positioned biased toward the top or the bottom, to be closer to an exterior surface of the housing 420 or gas sampling device 410. In some embodiments, the disposable sensor strip can be positioned less than 5 cm, 4 cm, 3 cm, 2 cm, 1 cm, 0.5 cm, 0.2 cm or less from exterior surface (or exterior wall) of the housing 420.

The docking station 430 is generally configured to collect data generated from testing the gas sample. The docking station 430 has a reading device 432 that can include circuitry to measure the capacitance of a plurality of graphene sensors. Aspects of circuitry to measure the capacitance of the graphene sensors is described in greater detail below. However, it will be appreciated that in some embodiments, such circuitry can all be disposed in the gas sampling device 410, can all be disposed in the docking station 430, or can be distributed with some components in the gas sampling device 410 and some components in the docking station 430. Indeed, in some cases there may not be a separate docking station and functionality attributed thereto herein can simply be integrated into the gas sampling device.

In various embodiments, the reading device 432 can also be configured to both baseline data and sample data from the disposable sensor test strip 440—where the term “baseline data” is defined as data collected before exposure of the disposable sensor test strip 440 to the gas sample or the patient or test subject and wherein the term “sample data” refers to data specific to the gas sample of the patient or test subject. In some cases the baseline data can reflect conditions of whatever gas happens to be in the testing chamber prior to obtaining a gas sample of a patient. However, in other embodiments, ambient air can purposefully be pushed through the testing chamber, and/or a particular reference gas sample of known composition can be put into the testing chamber for purposes of generating baseline data.

The docking station 430 is generally configured to be a docking location for the gas sampling device 410. The docking station 430 is generally configured to physically receive the gas sampling device 410. The docking station 430 can receive the gas sampling device 410 through a variety of structures and configurations that will be appreciated by those having ordinary skill in the art. In various embodiments the docking station 430 and the docking structure 421 of the gas sampling device 410 have a mating configuration by which the docking station 430 receives the docking structure 421 of the gas sampling device 410. In some such embodiments the docking station 430 and the docking structure 421 define an interference fit. However, in other embodiments, the docking station 430 can simply rest upon or in the docking structure 421. In some embodiments the docking station 430 and the docking structure 421 are configured to position the disposable sensor test strip 440 and the reading device 432 in sufficient proximity to accommodate transmission of data between the reading device 432 and disposable sensor test strip 440. In some embodiments the docking station and the docking structure are configured to position the disposable sensor test strip 440 and the reading device 432 within 6 cm, 5 cm, 4 cm, 3 cm, or 2 cm of each other, or even within 1 cm of each other.

The docking station 430 can have various additional components. In some embodiments the docking station 430 has a processor 436 and memory 435. The processor 436 and memory 435 can be configured to process and store data obtained from the tested gas sample. For example, the memory 435 can store baseline data locally and the processor 436 can be configured to remove collected baseline data from the tested gas data to obtain adjusted data. Such adjusted data can remove some impact of the ambient environment on the tested gas data. In another example, the processor can be configured to compare the adjusted data (or, in some embodiments the tested gas data) to known data indicative of one or more diseases. Such a comparison can be used to identify the presence of a particular disease using a comparative algorithm. In yet another example, the processor of the docking station 430 can be configured to identify a defect in the disposable sensor test strip 440. Example defects can include manufacturing defects and/or premature exposure to ambient gases. The docking station 430 can be configured to collect, save, and potentially transmit records of such defects.

The docking station 430 has networking hardware 434 in various embodiments. The networking hardware 434 can be configured to transmit data over a network to a remote system, including a cloud-based system. In some implementations the remote system can be a hospital, clinic, laboratory, or other location. In some embodiments the networking hardware 434 is configured to transmit data generated from testing the gas sample. The networking hardware 434 is configured to transmit baseline data in some embodiments. The networking hardware is configured to transmit adjusted data in some embodiments. In some embodiments the remote system analyzes the data it receives. For example, in some embodiments the remote system is configured to compare the adjusted data to known data indicative of a plurality of diseases. That comparison can identify the presence of a particular disease.

In some embodiments the docking station 430 has a user interface 438. The user interface 438 can be configured to communicate information to a user. For example, the user interface 438 can be configured to communicate an active data transmission, such as a data transmission between the docking station 430 and the gas sampling device 410 and/or between the docking station 430 and a network. In some embodiments the user interface 438 can be configured to communicate information about the current stage of the testing process, progress of the same, or what steps are next or what actions are required. For example, in some cases the user interface 438 can be configured to communicate that that the gas sampling device 410 is ready to receive a gas sample or that the docking station 430 has finished reading data from the gas sampling device 410. The user interface 438 can also be configured to communicate a defect in the sensor test strip. The user interface 438 can be configured to communicate through visual notification, audio notification, and the like. As a specific example, a flashing light can be used to indicate that the docking station 430 is transmitting data. The user interface 438 can include a light source such as an LED or similar light emitting device.

One example approach to using the system depicted in FIG. 4 will now be described. A disposable sensor test strip 440 is inserted into the gas sampling device 410 such that it is received by the gas testing chamber 426 defined by a housing of a gas sampling device. The gas sampling device 410 having the disposable sensor test strip 440 is docked to the docking station 430, and the reading device 432 of the docking station 430 reads baseline data from the disposable sensor test strip 440 through the housing 420 of the gas sampling device 410. The gas sampling device 410 is undocked from the docking station 430 after reading the baseline data, and a gas sample is received by the gas testing chamber such that the gas sample is brought into contact with the disposable sensor test strip 440. For example, the gas sampling device 410 may be physically grasped by a care provider and removed from the docking station 430 and physically handed to a patient or test subject who may then blow into the gas sampling device 410 to provide the gas sample to be analyzed. In other cases, the gas sampling device 410 may be held by the care provider instead of being held by the patient or test subject. The gas sampling device 410 can then be docked to the docking station 430 after receiving the gas sample, and the data from the tested gas is read from the disposable sensor test strip 440 by the reading device 432, wherein the adjusted data is read through the housing 420 of the gas sampling device 410. In various embodiments the disposable sensor test strip 440 is configured to be single-use. As such, the disposable sensor test strip 440 can be disposed of following the collection of sample gas data from the disposable sensor test strip 440. Various other methods of using the system depicted in FIG. 4 are also contemplated.

The measurement zones 442 can include a plurality of discrete binding detectors that can include one or more analyte binding receptors bound thereto. In some embodiments, all of the analyte binding receptors within a particular discrete binding detector can be the same with respect to their analyte binding properties. In other embodiments, at least some of the analyte binding receptors within a particular zone can be different from one another with respect to their analyte binding properties. In some embodiments, each discrete binding detector can be unique. In some embodiments, discrete binding detectors that are unique can be cross-reactive in that they bind to different portions or different configurations of the same chemical compound.

The plurality of graphene varactors can include those that are specific for different volatile organic compounds. In some embodiments, the plurality of graphene varactors can detect the presence of at least 5, 10, 15, 20, 30, 40 or more different volatile organic compounds. In some embodiments, the number of different volatile organic compounds detected by the graphene varactors can be in a range wherein any of the forgoing numbers can serve as the upper or lower bound of the range provided that the upper bound is greater than the lower bound.

As referenced above, the capacitance of the graphene sensor can be measured by delivering an excitation current at a particular voltage and/or over a range of voltages. Measuring the capacitance provides data that reflects the binding status of analytes to the graphene sensor. Various measurement circuitry can be used to measure the capacitance of the graphene sensor.

Referring now to FIG. 5 , a schematic diagram is shown of circuitry to measure the capacitance of a plurality of graphene sensors. The circuitry can include a capacitance to digital converter (CDC) 502 in electrical communication with a multiplexor 504. The multiplexor 504 can provide selective electrical communication with a plurality of graphene varactors 506. The other side of the graphene varactors 506 can be in electrical communication with a ground 508.

In some embodiments, the CDC 502 can be in electrical communication with a bus device 510. The bus device 510 can include various specific components, but in some embodiments can be selected from the group consisting of an I²C or an SPI. The bus device 510 can, in turn, be in electrical communication with a controller or processor. For example, the bus device 510 can be in electrical communication with a microcontroller 512. The microcontroller 512 can, in turn, be in communication with other components of the device or system. In will be appreciated that not all of the components illustrated in FIG. 5 may be separate from one another. On the contrary, various components can be integrated together, including, but not limited to, the multiplexor 504, the CDC 502, and the bus device 510.

In operation, the excitation signal (an alternating voltage) is applied to the selected capacitor through the multiplexor and the electronic charge required to charge and discharge the graphene varactor is measured to determine the capacitance. The amplitude of the excitation signal is fixed by the CDC 502. The bias voltage at which the capacitance is measured is equal to the average voltage of the excitation signal. An exemplary CDC for this type of configuration includes Texas Instruments model FDC1004. The FDC1004 has an integrated multiplexor and I²C. It will be appreciated that many other types of CDCs can also be used.

In some embodiments, the graphene varactors may not be grounded. The other side of the graphene varactors can be connected to another device. For example, in some embodiments the other side of the graphene varactors can be connected to an independent excitation output of the CDC or another component. In this case, an excitation signal (again, an alternating voltage) is applied to all of the capacitors in the sensor array, and electronic charge required to charge and discharge the selected graphene varactor is measured through the multiplexor to determine the capacitance. The amplitude of the excitation signal is set by the CDC. The bias voltage at which the capacitance is measured is equal to the difference between the bias voltage at the CDC input (via the multiplexor, usually equal to VCC/2, where VCC is the supply voltage) and the average voltage of the excitation signal. Since the excitation voltage is typically centered about VCC/2 for this type of CDC, the bias voltage is typically fixed at zero volts.

Referring now to FIG. 6 , a schematic diagram is shown of circuitry to measure the capacitance of a plurality of graphene sensors in accordance with another embodiment herein. The circuitry can include a capacitance to digital converter (CDC) 502 in electrical communication with a multiplexor 504. The multiplexor 504 can provide selective electrical communication with a plurality of graphene varactors 506. In this embodiment, the other side of the graphene varactors 506 can be in electrical communication with an independent excitation output of the CDC.

The change in capacitance of the graphene varactor based on analyte binding depends on the excitation voltage used to measure the capacitance. Because of this, a greater amount of information can be gathered by varying the voltage of the excitation signal across a range of voltages. Various techniques can be used to achieve this. However, in some embodiments, a pair of programmable digital to analog converters with different output voltages can be used in combination with a switch in order to achieve variation in the voltage of the excitation signal.

Referring now to FIG. 7 , a schematic diagram is shown of circuitry to measure the capacitance of a plurality of graphene sensors in accordance with another embodiment herein. The circuitry can include a capacitance to digital converter (CDC) 502 in electrical communication with a multiplexor 504. The multiplexor 504 can provide selective electrical communication with a plurality of graphene varactors 506. The connection to the other side of the graphene varactors 506 can be controlled by a switch 702 (as controlled by the CDC) and can provide selective electrical communication with a first digital to analog converter (DAC) 704 and a second digital to analog converter (DAC) 706. The other side of the DACs 704, 706 can be connected to a bus device 510, or in some cases, the CDC 502.

In this case, the excitation signal from the CDC controls the switch between the output voltages of the two programmable Digital to Analog Converters (DACs). The programmed voltage difference between the DACs determines the excitation amplitude, providing an additional programmable scale factor to the measurement and allowing measurement of a wider range of capacitances than specified by the CDC. The bias voltage at which the capacitance is measured is equal to the difference between the bias voltage at the CDC input (via the multiplexor, usually equal to VCC/2, where VCC is the supply voltage) and the average voltage of the excitation signal, which is programmable. In some embodiments, buffer amplifiers and/or bypass capacitance can be used at the DAC outputs to maintain stable voltages during switching. Many different ranges of DC bias voltages can be used. In some embodiments, the range of DC bias voltages can be from −3 V to 3 V, or from −1 V to 1 V, or from −0.5 V to 0.5 V.

Many different aspects can be calculated based on the capacitance data. For example, aspects that can be calculated include maximum slope of capacitance to voltage, change in maximum slope of capacitance to voltage over a baseline value, minimum slope of capacitance to voltage, change in minimum slope of capacitance to voltage over a baseline value, minimum capacitance, change in minimum capacitance over a baseline value, voltage at minimum capacitance (Dirac point), change in voltage at minimum capacitance, maximum capacitance, change in maximum capacitance, ratio of maximum capacitance to minimum capacitance, response time constants, and ratios of any of the foregoing between different graphene sensors and particularly between different graphene sensors having specificity for different analytes.

The above calculated aspects can be used for various diagnostic purposes. In some cases, the above calculated aspects can be indicative of the identity and/or concentrations of specific volatile organic components of a gas sample. As such, each of the calculated values above can serve as a distinct piece of data that forms part of a pattern for a given patient and/or given gas sample. As also described elsewhere herein, the pattern can then be matched against preexisting patterns, or patterns identified in real-time, derived from large, stored data sets through techniques such as machine learning or other techniques, wherein such patterns are determined to be characteristic of various conditions or disease states. The above calculated aspects can also be put to other purposes, diagnostic and otherwise.

In some cases calculations, such as those described above, can be performed by a controller circuit. The controller circuit can be configured to receive an electrical signal reflecting the capacitance of the graphene varactors. In some embodiments, the controller circuit can include a microcontroller to perform these calculations. In some cases the controller circuit can include a microprocessor in electrical communication with the measurement circuit. The microprocessor system can include components such as an address bus, a data bus, a control bus, a clock, a CPU, a processing device, an address decoder, RAM, ROM and the like. In some cases the controller circuit can include a calculation circuit (such as an application specific integrated circuit—ASIC) in electrical communication with the measurement circuit.

In addition, in some cases the system can include a nonvolatile memory where sensitivity calibration information for the particular sensor is stored. By way of example, the sensor could be tested in a production facility, where its sensitivity to various analytes such as VOC's can be determined and then stored on an EPROM or similar component. In addition or alternatively, sensitivity calibration information can be stored in a central database and referenced with a sensor serial number when patient data is sent to a central location for analysis and diagnosis. These components can be included with any of the pieces of hardware described herein.

In some embodiments herein, components can be configured to communicate over a network, such as the internet or a similar network. In various embodiments, a central storage and data processing facility can be included. In some embodiments, data gathered from sensors in the presence of the patient (local) can be sent to the central processing facility (remote) via the internet or a similar network, and the pattern from the particular patient being evaluated can be compared to those of thousands or millions of other patients, many of whom have been previously diagnosed with various conditions and wherein such condition data has been stored. Pattern matching algorithms can be used to find other patients or classes of patients (for example disease or condition specific classes) to which the current patient's pattern is most similar. Each class of patients can include a predetermined likelihood of having a given condition or disease state. In this manner, after pattern matching a likelihood of having a given condition or disease state can be provided back across the data network to the facility where the patient is currently at.

Methods

Embodiments herein can include various methods. Exemplary methods can include any of the approaches and/or operations described herein. In an embodiment, a method of measuring analyte presence on a graphene varactor is included. The method can include measuring a capacitance of the graphene varactor over a range of DC bias voltages, comparing the measured capacitance at one or more DC bias voltages to one or more corresponding baseline capacitance values and determining the presence or absence of an analyte based on the comparison.

In some embodiments, the method can further include determining one or more aspects including, but not limited to, maximum slope of capacitance to voltage, change in maximum slope of capacitance to voltage over a baseline value, minimum slope of capacitance to voltage, change in minimum slope of capacitance to voltage over a baseline value, minimum capacitance, change in minimum capacitance over a baseline value and voltage at minimum capacitance (Dirac point), change in voltage at minimum capacitance, maximum capacitance, change in maximum capacitance, ratio of maximum capacitance to minimum capacitance, response time constants, and ratios of any of the foregoing between different graphene sensors and particularly between different graphene sensors having specificity for different analytes.

In some embodiments, the method can include forming a capacitance to voltage curve from the measured capacitance of the graphene varactor over the range of DC bias voltages. In some embodiments, the method can include comparing the formed capacitance to voltage curve with a baseline capacitance to voltage curve. In some embodiments, the method can include distinguishing between different analytes binding to the graphene varactor. In some embodiments the method can further include measuring a capacitance of the graphene varactor over a range of DC bias voltages. In some embodiments, the range of DC bias voltages can be from −3 V to 3 V.

In some embodiments, the patient can be prompted to take a breath or gas test (where the test could be performed either in a non-clinical setting such as their home or where such a prompt could cause them to come to a clinical setting to take the test).

In some embodiments, a pattern including such things as sleep patterns (e.g. wearable, implant or non-contact in-home sensor), physiological data (autonomic tone measures), body weight (such as weight automatically measured by a mat in the house), activity levels (e.g. mobile device, wearable, implant or non-contact in-home sensor), etc. can be assessed, such as using an algorithm, and if the results of those factors so indicate, then the system can inform the user that they should administer or get a breath or gas test to detect early signs of heart failure decompensation. If a positive result, or data trends are beyond a normal range for the individual patient, then the system can inform the patient to seek medical care for early intervention.

In some embodiments, a pattern including things such as sleep patterns, autonomic tone, respiratory rate, respiratory sounds, activity levels, etc., can be used to recommend to the user that they should administer a breath test (or come to a clinic to get a breath test) to detect early signs of a COPD exacerbation or repeat exacerbation. If a positive result, or data trends beyond normal range for the individual patient, seek medical care and/or use prescribed pharmaceutical (e.g. bronchodilators, corticosteroids, etc.) for early intervention.

Beyond, heart failure decompensation and COPD, such patterns and prompts to the patient to get a breath test can also be used for diabetes management and inflammatory bowel diseases (also including data regarding dietary intake, autonomic tone, etc. in the pattern) to detect early signs of a flare-up.

EXAMPLES Example 1: Capacitance for a Graphene Varactor Over a Range of Voltages

A graphene varactor was manufactured consistent with that described in U.S. Publ. Appl. No. 2014/0145735.

A baseline capacitance to voltage curve was established by measuring capacitance over a range of excitation voltages while flushing the sensor with nitrogen gas using an LCR meter. The DC bias voltage ranged from −0.5 volts to 0.5 volts. Using the same LCR meter, capacitance values over the same bias voltage range were also measured while flushing the sensor with a combination of nitrogen gas and octanol vapor. The total flow rate was 0.5 liters per minute in each experiment, octanol concentration was approximately 3.6 parts per million in nitrogen, sensors were exposed to the nitrogen gas and octanol vapor mixture for approximately 5 minutes before measurement for equilibration, the AC excitation signal had amplitude 50 mV and frequency 500 kHz.

As shown in FIG. 8 , it can be seen that binding of octanol caused the capacitance to voltage curve to retain the same overall shape but be shifted to the right (e.g., the minimum capacitance occurred at a higher DC bias voltage).

Example 2: Capacitance for a Graphene Varactor Over a Range of Voltages

A graphene varactor was prepared as described in Example 1. A baseline capacitance to voltage curve was established by measuring capacitance over a range of excitation voltages using an LCR meter as described above in Example 1. The DC bias voltage ranged from −1 volt to 1 volt. Using the same LCR meter, capacitance values over the same bias voltage range were also measured while flushing the sensor with a combination of nitrogen gas and acetone vapor. Details were the same as descried above in Example 1, except that the acetone concentration was approximately 25,000 parts per million.

As shown in FIG. 9 , it can be seen that binding of acetone caused the capacitance to voltage curve to change shape in that the top portion of the curve was shifted to the right, but the bottom portion of the curve was shifted to the left.

Example 3: Capacitance for a Functionalized Graphene Varactor Over a Range of Voltages

A graphene varactor was prepared as described in Example 1. The graphene was then functionalized with pyrene-acetic acid by soaking the varactor in a 1 mM solution of pyrene acetic-acid in ethanol for 14 hours.

A baseline capacitance to voltage curve was established by measuring capacitance over a range of excitation voltages using an LCR meter as described above in Example 1. The DC bias voltage ranged from −1 volt to 1 volt. Using the same LCR meter, capacitance values over the same bias voltage range were also measured while flushing the sensor with: 1.) a combination of nitrogen gas and gaseous acetone, 1.) a combination of nitrogen gas and gaseous octane, and 3.) a combination of nitrogen gas and gaseous octanol.

As shown in FIG. 10 , it can be seen that binding of acetone caused the capacitance to voltage curve to shift sharply to the right, with the Dirac point increasing by approximately 0.1 volts. As shown in FIG. 11 , it can be seen that binding of octane caused relatively small changes in the capacitance to voltage curve, but the shift to the right made the binding detectable. As shown in FIG. 12 , it can be seen that binding of octanol caused relatively small changes in the capacitance to voltage curve, but the shift to the right made the binding detectable.

It should be noted that, as used in this specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the content clearly dictates otherwise. Thus, for example, reference to a composition containing “a compound” includes a mixture of two or more compounds. It should also be noted that the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise.

It should also be noted that, as used in this specification and the appended claims, the phrase “configured” describes a system, apparatus, or other structure that is constructed or configured to perform a particular task or adopt a particular configuration to. The phrase “configured” can be used interchangeably with other similar phrases such as arranged and configured, constructed and arranged, constructed, manufactured and arranged, and the like. “Circuitry” can include both hardwired circuitry for execution of particular operations as well as processors that are programmed to execute instructions to provide the same functionality.

All publications and patent applications in this specification are indicative of the level of ordinary skill in the art to which this specification pertains. All publications and patent applications are herein incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated by reference.

Aspects have been described with reference to various specific and preferred embodiments and techniques. However, it should be understood that many variations and modifications may be made while remaining within the spirit and scope herein. As such, the embodiments described herein are not intended to be exhaustive or to limit the scope to the precise forms disclosed herein. Rather, the embodiments are chosen and described so that others skilled in the art can appreciate and understand the principles and practices. 

The invention claimed is:
 1. A system for measuring analyte presence on a graphene varactor comprising: a capacitance to digital converter (CDC); a plurality of graphene varactors, each of the plurality of graphene varactors comprising an insulator layer, a gate electrode, a dielectric layer, a graphene layer, and a contact electrode; and a multiplexor configured to selectively provide electrical communication between the CDC and the plurality of graphene varactors; wherein the CDC is configured to measure the capacitance of the graphene varactor in response to an excitation signal over a plurality of DC bias voltages.
 2. The system of claim 1, wherein an excitation signal is applied to a selected graphene varactor through the multiplexor.
 3. The system of claim 1, the excitation signal comprising an alternating voltage.
 4. The system of claim 1, wherein the amplitude of the excitation signal is fixed by the CDC.
 5. The system of claim 1, further comprising a controller circuit configured to receive an electrical signal reflecting the capacitance of the graphene varactor.
 6. The system of claim 5, the controller circuit comprising a microcontroller.
 7. The system of claim 5, wherein the controller circuit is configured to calculate at least one parameter for the graphene varactor, the one parameter selected from the group consisting of maximum slope of capacitance to voltage; change in maximum slope of capacitance to voltage over a baseline value; minimum slope of capacitance to voltage; change in minimum slope of capacitance to voltage over a baseline value; minimum capacitance; change in minimum capacitance over a baseline value; voltage at minimum capacitance; change in voltage at minimum capacitance; maximum capacitance; change in maximum capacitance; ratio of maximum capacitance to minimum capacitance; response time constant; and ratios of any of the foregoing between the graphene varactor and a second graphene varactor.
 8. The system of claim 1, further comprising an electronic component in electrical communication with the controller circuit and the CDC, the electronic component selected from the group consisting of an I²C or an SPI.
 9. The system of claim 1, the graphene varactor comprising a functionalized graphene varactor.
 10. The system of claim 1, wherein the plurality of graphene varactors are grounded.
 11. The system of claim 1, wherein the plurality of graphene varactors are in electrical communication with an independent excitation output of the CDC.
 12. The system of claim 1, further comprising one or more programmable digital to analog converters (DACs) in series with the plurality of graphene sensors.
 13. The system of claim 1, further comprising a switch, the CDC in electrical communication with the switch and controlling the switch to selectively provide communication with output voltages of two programmable digital to analog converters (DACs), the programmed voltage difference between the DACs determining the excitation amplitude, and the difference between the programmed average voltage of the DAC s and the bias at the CDC input determining the DC bias.
 14. The system of claim 1, wherein a first graphene varactor of the plurality of graphene varactors is configured to detect a first volatile organic compound, wherein a second graphene varactor of the plurality of graphene varactors is configured to detect a second volatile organic compound, and wherein the first volatile organic compound is different from the second volatile organic compound.
 15. A method for measuring analyte presence on a graphene varactor comprising: selectively providing electrical communication between a CDC and a plurality of graphene varactors using a multiplexor, each of the plurality of graphene varactors comprising an insulator layer, a gate electrode, a dielectric layer, a graphene layer, and a contact electrode; measuring a capacitance of each of the graphene varactors over a range of DC bias voltages; and determining one or more aspects for each varactor selected from the group consisting of: maximum slope of capacitance to voltage; change in maximum slope of capacitance to voltage over a baseline value; minimum slope of capacitance to voltage; change in minimum slope of capacitance to voltage over a baseline value; minimum capacitance; change in minimum capacitance over a baseline value; voltage at minimum capacitance; change in voltage at minimum capacitance; maximum capacitance; change in maximum capacitance; ratio of maximum capacitance to minimum capacitance; response time constant; and ratios of any of the foregoing between two different graphene sensors.
 16. The method of claim 15, further comprising forming a capacitance to voltage curve from the measured capacitance of the graphene varactor over the range of DC bias voltages.
 17. The method of claim 15, further comprising comparing the formed capacitance to voltage curve with a baseline capacitance to voltage curve.
 18. The method of claim 17, further comprising distinguishing between different analytes binding to the graphene varactor.
 19. The method of claim 15, wherein the range of DC bias voltages is from −3 V to 3 V. 